I had a thought about the phone pings... Last year, Bowerman confirmed that he was telling search and rescue organisations not to waste their resources by looking for DeOrr, as they had done a very thorough search and were sure he was not there to be found. But this year, he has been talking about new searches. I think they got new evidence, maybe the cell phone pings, that has given them an idea of a new area to search. If they know the parents were at a certain area before they went to the store that day, maybe the dogs can find DeOrr's body.
Another thought. JM saying they went to the store to buy feminine products. Her mother even said JM texted her that morning and told her they were going to get feminine products - a bit of a strange thing to do, imo. Maybe they wanted to explain away a blood stain, or an area in the truck that had been cleaned that day with bleach, or maybe they even had the foresight to think of cadaver dogs and thought this could explain any hits.